The design of a tooling fixture is generally carried out in accordance with the specific requirements of a process after the mechanical machining process of the part has been developed. The process should be developed with full consideration of the possibility of the fixture being realised, while the design of the fixture can be modified if necessary. The quality of the design of workholding fixtures should be measured by whether it can ensure the quality of workpiece processing, high productivity, low cost, convenient chip removal, safe operation, labor-saving and easy manufacturing and maintenance.

I. Basic principles of tooling fixture design

1、To meet the stability and reliability of workpiece positioning in the process of use.

2、Sufficient load-bearing or clamping force to ensure that the workpiece is processed on the tooling fixture.

3, to meet the simple and rapid operation of the clamping process.

4. the perishable parts must be of a construction that can be replaced quickly and without the use of other tools when conditions are adequate.

5, to meet the reliability of repeated positioning of the fixture in the process of adjustment or replacement.

6、To avoid, as far as possible, complex and costly structures.

7. using standard parts as constituent Carbide Insert parts wherever possible.

8、To form the systemization and standardization of products within the company.

Second, the basic knowledge of tooling fixture design

An excellent machine tool fixture must meet the following basic requirements.

1, to ensure the machining accuracy of the workpiece to ensure the key to machining accuracy, the first lies in the correct selection of positioning benchmarks, positioning methods and positioning components, if necessary, positioning error analysis, but also pay attention to the structure of other components in the fixture on the impact of machining accuracy, to ensure that the fixture can meet the machining accuracy requirements of the workpiece.

2、Improve production efficiencyThe complexity of the special fixture should be adapted to the production capacity, and various fast and efficient clamping mechanisms should be used as far as possible to ensure easy operation, shorten auxiliary time and improve production efficiency.

3、Good process performance The structure of special fixtures should be simple and reasonable, easy to manufacture, assemble, adjust, inspect and maintain, etc.

4, the use of good performance fixtures should have sufficient strength and rigidity, operation should be easy, labor-saving, safe and reliable. Under the premise that the objective conditions allow and economical, pneumatic, hydraulic and other mechanized clamping devices should be used as far as possible to reduce the operator’s labor intensity. Workholding fixtures should also be convenient for chip removal. If necessary, chip removal structure can be set up to prevent chip damage to the positioning of the workpiece and damage to the tool, to prevent the accumulation of chips to bring a lot of heat and cause deformation of the process system.

5、Good economy special fixture should adopt standard components and standard structure as far as possible, and strive for simple structure and easy manufacturing to reduce the manufacturing cost of the fixture. Therefore, the design should be based on orders and production capacity to make the necessary technical and economic analysis of the fixture scheme in order to improve the economic efficiency of the fixture in production.

III. Overview of standardisation of tooling fixture design

1、Basic methods and steps of tooling fixture design

a) Preparation before design The original information for the design of tooling fixtures includes the following.

Design notice, finished parts diagram, blank diagram and process route and other technical information, to understand the processing technology requirements of each process, positioning and clamping scheme, the processing content of the previous process, the blank situation, the machine tools used in processing, tools, inspection gauges, machining allowance and cutting dosage, etc..

b) To understand the production batch and the need for fixtures and fittings.

c) To understand the main technical parameters, performance, specifications, accuracy of the machine tool used and the connection dimensions of the structure of the part connected to the fixture.

d) stock of standard materials for the fixture.

2. Considerations for the design of workholding jigs

Fixture design is generally a single structure, giving the impression that the structure is not very complex, especially now that hydraulic fixtures are in vogue, making its original mechanical structure greatly simplified, but if the design process is not considered in detail will inevitably lead to unnecessary trouble: a) the raw material of the part to be machined

a) The blank allowance of the machined part. This results in oversized blanks and interference. This is why it is important to prepare a blank drawing before designing. Allow sufficient space.

b) Blank allowance for the part to be machined. Causes oversize of blanks and produces interference. So prepare the blank drawing before designing. Allow sufficient space.

c) Smooth chip evacuation of the fixture. Design due to the limited processing space of the machine tool, fixtures are often designed to be more compact space, which is often ignored in the machining process generated by the chip in the fixture dead-end storage, including the chip liquid outflow is not smooth, to bring a lot of trouble later processing. Therefore, the problems that arise during machining should be considered at the beginning of the actual process, after all, the fixture is designed to improve efficiency and facilitate operation.

d) The basic theoretical principles of fixture design. Every fixture has to go through countless clamping and unclamping actions, so it may all meet the user’s requirements at the beginning, but a fixture should have its accuracy maintained, so don’t design something that goes against the principle. Even if you get away with it, it will not be sustainable in the long term. A good design should stand up to the test of time.

e) Replaceability of the positioning elements. Positioning elements are subject to severe wear and tear, so quick and easy replacement should be considered. Do not design for larger parts.

Experience in fixture design is important, sometimes design is one thing and in practice it is another, so good design is a process of accumulation and conclusion.

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State: Canton
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